WHEN EXACTLY WERE YOU BORN? COMPARING EXACT DATE OF BIRTH AND DATE OF BIRTH PROXIES IN THE MARKETSCAN MULTI-STATE MEDICAID DATABASE
Author(s)
Elizabeth Packnett, MPH, George Shrady, MS, Liisa Palmer, PhD;
MarketScan by Merative, Ann Arbor, MI, USA
MarketScan by Merative, Ann Arbor, MI, USA
OBJECTIVES: For data confidentiality reasons, exact date of birth (DOB) is regularly unavailable in deidentified databases but many analyses, including safety studies, depend on accurate assessment of age. In infants, DOB can be estimated using proxies, but these proxies often incorrectly identify the DOB. Incorrectly assigned DOB proxies can result in misclassification of critical time periods for time to vaccination, hospitalization, or other outcomes in the first year of life. This study’s objective was to compare exact DOB to DOB proxies in the MarketScan Multi-State Medicaid Database.
METHODS: Infants with a DOB between 1/1/2020 and 12/31/2023 were identified in the MarketScan Multi-State Medicaid Database. All infants were required to have Medicaid enrollment during the calendar year of birth. Two DOB proxies were assigned using 1) date of infant’s first medical or pharmacy claim and 2) enrollment start date. Each proxy was compared to the exact DOB. Days between exact DOB and each proxy were calculated overall and separately for proxies before and after the exact DOB.
RESULTS: 966,694 infants with enrollment during their birth year were included in the study. Most could be assigned a DOB proxy using claim date (94.9%) or enrollment date (99.8%). About 12% (11.9%) were assigned an incorrect DOB using claim date; nearly 40% (39.2%) were assigned an incorrect DOB using enrollment date. For infants with incorrectly assigned DOB, the mean days between the exact DOB and proxy was 54.4 (SD: 75.0) using claim date and 29.2 (SD: 45.6) using enrollment date.
CONCLUSIONS: Though DOB proxies can be used to estimate DOB when exact DOB is not available, when proxies incorrectly estimate DOB it is by 29-54 days on average. This discrepancy may result in the misclassification of infant outcomes, particularly during the neonatal period.
METHODS: Infants with a DOB between 1/1/2020 and 12/31/2023 were identified in the MarketScan Multi-State Medicaid Database. All infants were required to have Medicaid enrollment during the calendar year of birth. Two DOB proxies were assigned using 1) date of infant’s first medical or pharmacy claim and 2) enrollment start date. Each proxy was compared to the exact DOB. Days between exact DOB and each proxy were calculated overall and separately for proxies before and after the exact DOB.
RESULTS: 966,694 infants with enrollment during their birth year were included in the study. Most could be assigned a DOB proxy using claim date (94.9%) or enrollment date (99.8%). About 12% (11.9%) were assigned an incorrect DOB using claim date; nearly 40% (39.2%) were assigned an incorrect DOB using enrollment date. For infants with incorrectly assigned DOB, the mean days between the exact DOB and proxy was 54.4 (SD: 75.0) using claim date and 29.2 (SD: 45.6) using enrollment date.
CONCLUSIONS: Though DOB proxies can be used to estimate DOB when exact DOB is not available, when proxies incorrectly estimate DOB it is by 29-54 days on average. This discrepancy may result in the misclassification of infant outcomes, particularly during the neonatal period.
Conference/Value in Health Info
2026-05, ISPOR 2026, Philadelphia, PA, USA
Value in Health, Volume 29, Issue S6
Code
SA7
Topic
Study Approaches
Disease
SDC: Pediatrics